Aluminum hydroxide

ABSTRACT

Aluminum hydroxide flame-retardants and their use.

FIELD OF THE INVENTION

The present invention relates to novel aluminum hydroxide flameretardants and their use.

BACKGROUND OF THE INVENTION

Aluminum hydroxide has a variety of alternative names such as aluminumhydrate, aluminum trihydrate etc., but is commonly referred to as ATH.ATH particles find use as a filler in many materials such as, forexample, plastics, rubber, thermosets, papers, etc. These products finduse in diverse commercial applications such as wire and cable compounds,conveyor belts, thermoplastics moldings, wall claddings, floorings, etc.ATH is typically used to improve the flame retardancy of such materialsand also acts as a smoke suppressant.

Methods for the synthesis of ATH are well known in the art. For example,see EP 1 206 412 B1 describes the production of fine precipitatedaluminum hydroxide grades wherein a pregnant liquor obtained from theBayer process is seeded with bayerite crystals. By using controlledconditions during crystallization, tailor made ATH grades withconsistent product qualities can be produced. The ATH grades aretypically distinguished by two important characteristics, the medianparticle size, commonly referred to as d₅₀, and the specific surface,commonly referred to as the BET specific surface area, and these twocharacteristics are major criteria to select an ATH for a specificapplication.

However, ATH's are not selected solely on their d₅₀ and/or BET specificsurface areas. To the contrary, ATH's are also selected based on thecompounding performance of the ATH-containing resin, and the demand forbetter compounding performance has increased. The compoundingperformance of an ATH-containing resin is generally determined byviewing the power draw on the motor of the compounding machine used incompounding the ATH-containing resin. Less variations of the power drawon the motor of the compounding machine translates to less wear on thecompounder engine, better compounded resins, and higher throughputs ofthe ATH-containing resin during compounding.

Thus, because there is a demand for higher throughputs in thecompounding of ATH-flame retarded resins and the performance of theATH-flame retarded synthetic resin is a critical attribute that islinked to the ATH, compounders would benefit from, and thus there is ademand for, an ATH which, during compounding, would allow for higherthroughputs in compounding machines like Buss Ko-kneaders, twin-screwextruders or other suitable machines.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows the specific pore volume V as a function of the appliedpressure for the second intrusion test run and an ATH grade no. 1, anATH according to the present invention, in comparison with standardgrades.

FIG. 2 shows the specific pore volume V plotted against the pore radiusr for the second intrusion test run and an ATH grade no. 1, an ATHaccording to the present invention, in comparison with standard grades.

FIG. 3 shows the normalized specific pore volume for an ATH grade no. 1,an ATH according to the present invention, in comparison with standardgrades, the graph was generated with the maximum specific pore volumefor each ATH grade set at 100%, and the other specific volumes of thecorresponding ATH grade were divided by this maximum value.

FIG. 4 shows the specific pore volume V as a function of the appliedpressure for the second intrusion test run and an ATH grade no. 2, anATH according to the present invention, in comparison with standardgrades.

FIG. 5 shows the specific pore volume V plotted against the pore radiusr for the second intrusion test run and an ATH grade no. 2, an ATHaccording to the present invention, in comparison with standard grades.

FIG. 6 shows the normalized specific pore volume for an ATH grade no. 2,an ATH according to the present invention, in comparison with standardgrades, the graph was generated with the maximum specific pore volumefor each ATH grade set at 100%, and the other specific volumes of thecorresponding ATH grade were divided by this maximum value.

FIG. 7 shows the specific pore volume V as a function of the appliedpressure for the second intrusion test run and an ATH grade no. 3, anATH according to the present invention, in comparison with a standardgrade.

FIG. 8 shows the specific pore volume V plotted against the pore radiusr for the second intrusion test run and an ATH grade no. 3, an ATHaccording to the present invention, in comparison with a standard grade.

FIG. 9 shows the normalized specific pore volume for an ATH grade no. 3,an ATH according to the present invention, in comparison with standardgrades, the graph was generated with the maximum specific pore volumefor each ATH grade set at 100%, and the other specific volumes of thecorresponding ATH grade were divided by this maximum value.

FIG. 10 shows the power draw on the motor of a discharge extruder forthe inventive aluminum hydroxide grade no. 1 used in the Example 1.

FIG. 11 shows the power draw on the motor of a discharge extruder forthe comparative aluminum hydroxide grade OL-104 LE used in Example 2.

SUMMARY OF THE INVENTION

Higher compounding throughputs can be achieved through the use of ATH'swith better wettability in the selected synthetic material. An ATH witha poor wettability in the synthetic resin leads to higher variations inthe power draw of the compounder motor during compounding, which in turnleads to, at best, a moderate compound quality, low throughputs, and,over time, can represent a considerable risk for damage to the engine ofthe compounding machine.

In one embodiment, the present invention relates to ATH particles havinga median pore radius in the range of from about 0.09 to about 0.33 μm.

In another embodiment, the present invention relates to ATH particleshaving a median pore radius in the range of from about 0.09 to about0.33 μm and a maximum specific pore volume of from about 300 to about700 mm³/g.

In yet another embodiment, the present invention relates to ATHparticles having:

a d₅₀ in the range of from 0.5 to about 2.5 μm;

a BET specific surface area of from about 1 to about 15 m²/g; and

a median pore radius in the range of from about 0.09 to about 0.33 μm.

In still yet another embodiment, the present invention relates to ATHparticles having:

i) a BET specific surface area of from about 3 to about 6 m²/g; and

-   -   a maximum specific pore volume of from about 390 to about 480        mm³/g;

or

ii) a BET specific surface area of from about 6 to about 9 m²/g; and

-   -   a maximum specific pore volume of from about 400 to about 600        mm³/g or

iii) a BET specific surface area of from about 9 to about 15 m²/g; and

-   -   a maximum specific pore volume of from about 300 to about 700        mm³/g.

In yet another embodiment, the present invention relates to a flameretarded polymer formulation comprising at least one synthetic resin anda flame retarding amount of ATH particles having a median pore radius inthe range of from about 0.09 to about 0.33 μm.

DETAILED DESCRIPTION OF THE INVENTION

The wettability of ATH particles with resins depends on the morphologyof the ATH particles, and the inventors hereof have unexpectedlydiscovered that the ATH particles according to the present inventionhave an improved wettability in relation to ATH particles currentlyavailable. While not wishing to be bound by theory, the inventors hereofbelieve that this improved wettability is attributable to an improvementin the morphology of the ATH particles disclosed herein.

Again, while not wishing to be bound by theory, the inventors hereofbelieve that this improved morphology is attributable to the specificpore volume and/or the median pore radius (“r₅₀”) of the ATH productparticles of the present invention. The inventors hereof believe that,for a given polymer molecule, an ATH product having a higher structuredaggregate contains more and bigger pores and seems to be more difficultto wet, leading to difficulties (higher variations of the power draw onthe motor) during compounding in kneaders like Buss Ko-kneaders ortwin-screw extruders or other machines known in the art and used to thispurpose. Therefore, the inventors hereof have discovered that an ATHfiller characterized by smaller median pore sizes and/or lower totalpore volumes correlates with an improved wetting with polymericmaterials and thus results in improved compounding behavior. i.e. lessvariations of the power draw of the engines (motors) of compoundingmachines used to compound a flame retarded resin containing the ATHfiller.

ATH Particles of the Present Invention

The aluminum hydroxide particles according to the present invention arecharacterized by a certain median pore radius and/or a lower totalspecific pore volume at 1000 bar, V_(max), as determined by mercuryporosimetry. The r₅₀ and the V_(max) of the ATH particles according tothe present invention can be derived from mercury porosimetry. Thetheory of mercury porosimetry is based on the physical principle that anon-reactive, non-wetting liquid will not penetrate pores untilsufficient pressure is applied to force its entrance. Thus, the higherthe pressure necessary for the liquid to enter the pores, the smallerthe pore size. A smaller pore size and/or a lower total specific porevolume was found to correlate to better wettability of the aluminumhydroxide particles. The pore size of the aluminum hydroxide particlesof the present invention can be calculated from data derived frommercury porosimetry using a Porosimeter 2000 from Carlo ErbaStrumentazione, Italy. According to the manual of the Porosimeter 2000,the following equation is used to calculate the pore radius r from themeasured pressure p: r=−2 γ cos(θ)/p; wherein θ is the wetting angle andγ is the surface tension. The measurements taken herein used a value of141.3° for θ and γ was set to 480 dyn/cm.

In order to improve the repeatability of the measurements, the pore sizeof the ATH particles was calculated from the second ATH intrusion testrun, as described in the manual of the Porosimeter 2000. The second testrun was used because the inventors observed that an amount of mercuryhaving the volume V₀ remains in the sample of the ATH particles afterextrusion, i.e. after release of the pressure to ambient pressure. Thus,the r₅₀ can be derived from this data as explained below with referenceto FIGS. 1, 2, and 3.

In the first test run, an ATH sample was prepared as described in themanual of the Porosimeter 2000, and the pore volume was measured as afunction of the applied intrusion pressure p using a maximum pressure of1000 bar. The pressure was released and allowed to reach ambientpressure upon completion of the first test run. A second intrusion testrun (according to the manual of the Porosimeter 2000) utilizing the sameATH sample, unadulterated, from the first test run was performed, wherethe measurement of the specific pore volume V(p) of the second test runtakes the volume V₀ as a new starting volume, which is then set to zerofor the second test run.

In the second intrusion test run, the measurement of the specific porevolume V(p) of the sample was again performed as a function of theapplied intrusion pressure using a maximum pressure of 1000 bar. FIG. 1shows the specific pore volume V as a function of the applied pressurefor the second intrusion test nm and an ATH, grade no. 1, according tothe present invention in comparison with current commercially availableATH products. The pore volume at 1000 bar, i.e. the maximum pressureused in the measurement, is referred to as V_(max) herein.

From the second ATH intrusion test run, the pore radius r was calculatedby the Porosimeter 2000 according to the formula r=−2 γ cos(θ)/p;wherein θ is the wetting angle, γ is the surface tension and p theintrusion pressure. For all r-measurements taken herein, a value of141.3° for θ was used and γ was set to 480 dyn/cm. The specific porevolume can thus be plotted against the pore radius r. FIG. 2 shows thespecific pore volume V of the second intrusion test run (using the samesample) plotted against the pore radius r.

FIG. 3 shows the normalized specific pore volume of the second intrusiontest run plotted against the pore radius r, i.e. in this curve, themaximum specific pore volume of the second intrusion test run, V_(max),was set to 100% and the other specific volumes for that particular ATHwere divided by this maximum value. The pore radius at 50% of therelative specific pore volume, by definition, is called median poreradius r₅₀ herein. For example, according to FIG. 3, the median poreradius r₅₀ for an ATH according to the present invention, i.e. Inventive1, is 0.277 μm.

The procedure described above was repeated using a sample of ATHparticles according to the present invention, and the ATH particles werefound to have an r₅₀, i.e. a pore radius at 50% of the relative specificpore volume, in the range of from about 0.09 to about 0.33 μm. Inpreferred embodiments of the present invention, the r₅₀ of the ATHparticles is in the range of from about 0.20 to about 0.33 μm, morepreferably in the range of from about 0.2 to about 0.3 μm. In otherpreferred embodiments, the r₅₀ is in the range of from about 0.185 toabout 0.325 μm, more preferably in the range of from about 0.185 toabout 0.25 μm. In still other preferred embodiments, the r₅₀ is in therange of from about 0.09 to about 0.21 μm, more preferably in the rangeof from about 0.09 to about 0.165 μm.

The ATH particles of the present invention can also be characterized ashaving a V_(max), i.e. maximum specific pore volume at 1000 bar, in therange of from about 300 to about 700 mm³/g. In preferred embodiments ofthe present invention, the V_(max) of the ATH particles is in the rangeof from about 390 to about 480 mm³/g, more preferably in the range offrom about 410 to about 450 mm³/g. In other preferred embodiments, theV_(max) is in the range of from about 400 to about 600 mm³/g, morepreferably in the range of from about 450 to about 550 mm³/g. In yetother preferred embodiments, the V_(max) is in the range of from about300 to about 700 mm³/g, more preferably in the range of from about 350to about 550 mm³/g.

The ATH particles of the present invention can also be characterized ashaving an oil absorption, as determined by ISO 787-5:1980 of in therange of from about 1 to about 35%. In some preferred embodiments, theATH particles of the present invention are characterized as having anoil absorption in the range of from about 23 to about 30%, morepreferably in the range of from about 25% to about 28%. In otherpreferred embodiments, the ATH particles of the present invention arecharacterized as having an oil absorption in the range of from about 25%to about 32%, more preferably in the range of from about 26% to about30%. In yet other preferred embodiments, the ATH particles of thepresent invention are characterized as having an oil absorption in therange of from about 25 to about 35% more preferably in the range of fromabout 27% to about 32%. In other embodiments, the oil absorption of theATH particles according to the present invention are in the range offrom about 19% to about 23%, and in still other embodiments, the oilabsorption of the ATH particles according to the present invention is inthe range of from about 21% to about 25%.

The ATH particles according to the present invention can also becharacterized as having a BET specific surface area, as determined byDIN-66132, in the range of from about 1 to 15 m²/g. In preferredembodiments, the ATH particles according to the present invention have aBET specific surface in the range of from about 3 to about 6 m²/g, morepreferably in the range of from about 3.5 to about 5.5 m²/g. In otherpreferred embodiments, the ATH particles according to the presentinvention have a BET specific surface of in the range of from about 6 toabout 9 m²/g, more preferably in the range of from about 6.5 to about8.5 m²/g. In still other preferred embodiments, the ATH particlesaccording to the present invention have a BET specific surface in therange of from about 9 to about 15 m²/g, more preferably in the range offrom about 10.5 to about 12.5 m²/g.

The ATH particles according to the present invention can also becharacterized as having a d₅₀ in the range of from about 0.5 to 2.5 μm.In preferred embodiments, the ATH particles according to the presentinvention have a d₅₀ in the range of from about 1.5 to about 2.5 μm,more preferably in the range of from about 1.8 to about 2.2 μm. In otherpreferred embodiments, the ATH particles according to the presentinvention have a d₅₀ in the range of from about 1.3 to about 2.0 μm,more preferably in the range of from about 1.4 to about 1.8 μm. In stillother preferred embodiments, the ATH particles according to the presentinvention have a d₅₀ in the range of from about 0.9 to about 1.8 μm,more preferably in the range or from about 1.1 to about 1.5 μm.

It should be noted that all particle diameter measurements, i.e. d₅₀,disclosed herein were measured by laser diffraction using a Cilas 1064 Llaser spectrometer from Quantachrome. Generally, the procedure usedherein to measure the d₅₀, can be practiced by first introducing asuitable water-dispersant solution (preparation see below) into thesample-preparation vessel of the apparatus. The standard measurementcalled “Particle Expert” is then selected, the measurement model “Range1” is also selected, and apparatus-internal parameters, which apply tothe expected particle size distribution, are then chosen. It should benoted that during the measurements the sample is typically exposed toultrasound for about 60 seconds during the dispersion and during themeasurement. After a background measurement has taken place, from about75 to about 100 mg of the sample to be analyzed is placed in the samplevessel with the water/dispersant solution and the measurement started.The water/dispersant solution can be prepared by first preparing aconcentrate from 500 g Calgon, available from KMF Laborchemie, with 3liters of CAL Polysalt, available from BASF. This solution is made up to10 liters with deionized water. 100 ml of this original 10 liters istaken and in turn diluted further to 10 liters with deionized water, andthis final solution is used as the water-dispersant solution describedabove.

Making of ATH Particles of the Present Invention

The ATH particles of the present invention can be made by severalprocesses such as, for example, by spray drying a slurry produced from,for example, a process such as that described below, and dry-milling;mill drying a slurry or filter cake produced from, for example, aprocess such as that described below, with optional deagglomeration; andwet milling followed by spray drying. For example, see those processesdisclosed in commonly-owned co-pending applications 60/818,632;60/899,316; 60/891,746; 60/891,745; 60/818,633; and 60/818,670, whichare all incorporated herein by reference in their entirety. In someembodiments, the ATH particles of the present invention are made by aprocess comprising wet-milling an ATH slurry containing in the range offrom about 1 to about 40 wt. %, based on the total weight of the slurry,ATH particles. “Wet-milling” as used herein is meant to refer to thecontacting of the ATH slurry with a milling media in the presence of aliquid. Liquids suitable for use in wet-milling herein are any liquidsthat do not substantially solubilize the ATH, preferably the liquid iswater. In some wet-milling processes suitable for producing ATHparticles according to the present invention, the slurry may alsocontain a suitable dispersing agent.

The milling media used in the wet-milling can be balls, rods, or othershapes made of various materials. Some common materials of constructionfor the milling media include ceramic, steel, aluminum, glass orzirconium oxide (ZrO₂). For ceramic milling media, the density should beabove 2.5 g/cm³. Preferably, metal-based milling media with a density ofat least 1.5 g/cm³ are used, preferably in the range of from about 2.0to about 2.5 g/cm³. In preferred wet-milling processes, the millingmedia is selected from those media having a general spherical shape,more preferably spherical milling media having a diameter in the rangeof from about 0.1 mm to about 1.0 mm, more preferably the milling mediais a zirconium milling media, most preferably zirconium oxide.

The ATH slurry that is wet-milled in the practice of the presentinvention can be obtained from any process used to produce ATHparticles. Preferably the slurry is obtained from a process thatinvolves producing ATH particles through precipitation and filtration.

The wet-milling of the ATH slurry results in a milled ATH slurry that isrecovered from the wet-milling operation by any technique commonly usedto recover milled products from wet-milling operations. The recoveredmilled ATH slurry is then subjected to drying. Any drying method knownin the art that is suitable for drying an ATH slurry can be used.Non-limiting examples of drying methods include spray drying, usingspray driers such as those available from the Niro company/Sweden, flashdrying or cell mill drying using mill-driers commercially available fromthe Atritor company or those available from Altenburger MaschinenJaeckering, GmbH. In some embodiments, the milled ATH slurry is spraydried, and in other embodiments, the milled ATH slurry is dried using amill-drier.

Use as a Flame Retardant

The ATH particles according to the present invention can be used as aflame retardant in a variety of synthetic resins. Non-limiting examplesof thermoplastic resins where the ATH particles find use includepolyethylene, ethylene-propylene copolymer, polymers and copolymers ofC₂ to C₈ olefins (α-olefin) such as polybutene, poly(4-methylpentene-1)or the like, copolymers of these olefins and diene, ethylene-acrylatecopolymer, polystyrene, ABS resin, AAS resin, AS resin. MBS resin,ethylene-vinyl chloride copolymer resin, ethylene-vinyl acetatecopolymer resin, ethylene-vinyl chloride-vinyl acetate graft polymerresin, vinylidene chloride, polyvinyl chloride, chlorinatedpolyethylene, vinyl chloride-propylene copolymer, vinyl acetate resin,phenoxy resin, and the like. Further examples of suitable syntheticresins include thermosetting resins such as epoxy resin, phenol resin,melamine resin, unsaturated polyester resin, alkyd resin and urea resinand natural or synthetic rubbers such as EPDM, butyl rubber, isoprenerubber, SBR, NIR, urethane rubber, polybutadiene rubber, acrylic rubber,silicone rubber, fluoro-elastomer, NBR and chloro-sulfonatedpolyethylene are also included. Further included are polymericsuspensions (latices).

Preferably, the synthetic resin is a polyethylene-based resins such ashigh-density polyethylene, low-density polyethylene, linear low-densitypolyethylene, ultra low-density polyethylene, EVA (ethylene-vinylacetate resin), EEA (ethylene-ethyl acrylate resin), EMA(ethylene-methyl acrylate copolymer resin), EAA (ethylene-acrylic acidcopolymer resin) and ultra high molecular weight polyethylene; andpolymers and copolymers of C₂ to C₈ olefins (α-olefin) such aspolybutene and poly(4-methylpentene-1), polyvinyl chloride and rubbers.In a more preferred embodiment, the synthetic resin is apolyethylene-based resin.

The inventors have discovered that by using the ATH particles accordingto the present invention as flame retardants in synthetic resins, bettercompounding performance, of the aluminum hydroxide containing syntheticresin can be achieved. The better compounding performance is highlydesired by those compounders, manufactures, etc. producing highly tilledflame retarded compounds and final extruded or molded articles out ofATH-containing synthetic resins. By highly filled, it is meant thosecontaining the flame retarding amount of ATH, discussed below.

By better compounding performance, it is meant that variations in theamplitude of the energy level of compounding machines like BussKo-kneaders or twin screw extruders needed to mix a synthetic resincontaining ATH particles according to the present invention are smallerthan those of compounding machines mixing a synthetic resin containingconventional ATH particles. The smaller variations in the energy levelallows for higher throughputs of the ATH-containing synthetic resins tobe mixed or extruded and/or a more uniform (homogenous) material.

Thus, in one embodiment, the present invention relates to a flameretarded polymer formulation comprising at least one synthetic resin,selected from those described above, in some embodiments only one and aflame retarding amount of ATH particles according to the presentinvention, and extruded and/or molded article made from the flameretarded polymer formulation.

By a flame retarding amount of the ATH, it is generally meant in therange of from about 5 wt % to about 90 wt %, based on the weight of theflame retarded polymer formulation, and more preferably from about 20 wt% to about 70 wt %, on the same basis. In a most preferred embodiment, aflame retarding amount is from about 30 wt % to about 65 wt % of the ATHparticles, on the same basis.

The flame retarded polymer formulation can also contain other additivescommonly used in the art. Non-limiting examples of other additives thatare suitable for use in the flame retarded polymer formulations of thepresent invention include extrusion aids such as polyethylene waxes,Si-based extrusion aids, fatty acids; coupling agents such as amino-,vinyl- or alkyl silanes or maleic acid grafted polymers; sodium stearateor calcium sterate; organoperoxides; dyes; pigments; fillers; blowingagents; deodorants; thermal stabilizers; antioxidants; antistaticagents; reinforcing agents; metal scavengers or deactivators; impactmodifiers; processing aids; mold release aids, lubricants; anti-blockingagents; other flame retardants; UV stabilizers; plasticizers; flow aids;and the like. If desired, nucleating agents such as calcium silicate orindigo can be included in the flame retarded polymer formulations also.The proportions of the other optional additives are conventional and canbe varied to suit the needs of any given situation.

The methods of incorporation and addition of the components of theflame-retarded polymer formulation is conducted is not critical to thepresent invention and can be any known in the art so long as the methodselected involves substantially uniform mixing. For example, each of theabove components, and optional additives if used, can be mixed using aBuss Ko-kneader, internal mixers, Farrel continuous mixers or twin screwextruders or in some cases also single screw extruders or two rollmills. The flame retarded polymer formulation can then be molded in asubsequent processing step, if so desired. In some embodiments,apparatuses can be used that thoroughly mix the components to form theflame retarded polymer formulation and also mold an article out of theflame retarded polymer formulation. Further, the molded article of theflame-retardant polymer formulation may be used after fabrication forapplications such as stretch processing, emboss processing, coating,printing, plating, perforation or cutting. The molded article may alsobe affixed to a material other than the flame-retardant polymerformulation of the present invention, such as a plasterboard, wood, ablock board, a metal material or stone. However, the kneaded mixture canalso be inflation-molded, injection-molded, extrusion-molded,blow-molded, press-molded, rotation-molded or calender-molded.

In the case of an extruded article, any extrusion technique known to beeffective with the synthetic resins mixture described above can be used.In one exemplary technique, the synthetic resin, aluminum hydroxideparticles, and optional components, if chosen, are compounded in acompounding machine to form a flame-retardant resin formulation asdescribed above. The flame-retardant resin formulation is then heated toa molten state in an extruder, and the molten flame-retardant resinformulation is then extruded through a selected die to form an extrudedarticle or to coat for example a metal wire or a glass fiber used fordata transmission.

The above description is directed to several embodiments of the presentinvention. Those skilled in the art will recognize that other means,which are equally effective, could be devised for carrying out thespirit of this invention. It should also be noted that preferredembodiments of the present invention contemplate that all rangesdiscussed herein include ranges from any lower amount to any higheramount. For example, a flame retarding amount of the ATH, can alsoinclude amounts in the range of about 70 to about 90 wt. %, 20 to about65 wt. %, etc. The following examples will illustrate the presentinvention, but are not meant to be limiting in any manner.

EXAMPLES

The r₅₀ and V_(max) described in the examples below was derived frommercury porosimetry using a Porosimeter 2000, as described above. Alld₅₀, BET, oil absorption, etc., unless otherwise indicated, weremeasured according to the techniques described above. Also, the term“inventive aluminum hydroxide grade” and “inventive filler” as used inthe examples is meant to refer to an ATH according to the presentinvention, and “comparative aluminum hydroxide grade” is meant to referto an ATH that is commercially available and not according to thepresent invention.

Example 1

By seeding a pregnant sodium aluminate liquor as e.g. disclosed in EP 1206 412 B1, a synthetic aluminium hydroxide grade with a median particlesize of d₅₀=2.43 μm and a specific surface of 2.6 m²/g was produced.Common separation and filtration techniques were used to separate saidsynthetic aluminum hydroxide; after subsequent washing steps on beltfilters, the resulting aluminum hydroxide filter paste with a solidcontent of 61 wt. % was liquefied by adding a sufficient quantity of thedispersing agent Antiprex A40 from Ciba until the viscosity of theslurry was about 150 cPoise. The slurry was fed into a pearl mill, typeKD 200 D from Bachofen/Switzerland. This mill contained 270 kg of smallbeads made of zirconium oxide with a diameter of 0.6 mm. The throughputof the mill was controlled so that after drying by means of a Niro F 100spray drier and conveying of the inventive aluminum hydroxide into asilo the resulting d₅₀ was 1.89 μm and the specific surface was 4.9m²/g. In the present example, the throughput was about 3 m³/h. FIG. 1shows the specific pore volume of the inventive aluminum hydroxide gradeno. 1 as a function of the applied pressure of the second intrusion testrun. FIG. 2 shows the specific pore volume of the inventive aluminumhydroxide grade no. 1 as a function of the pore radius. FIG. 3 shows thenormalized specific pore volume of the inventive aluminum hydroxidegrade no. 1 as a function of the pore radius on a linear scale. Theproduct properties of the inventive aluminum hydroxide grade no. 1 arecontained in Table 1, below.

Example 2 Comparative

The product properties of the comparative aluminum hydroxide gradeMartinal OL-104 LE produced by Martinswerk GmbH and the productproperties of two competitive aluminum hydroxide grades “Competitive 1”and “Competitive 2” are also shown in Table 1.

TABLE 1 Maximum Median Specific Median pore specific pore particle BETradius (“r₅₀”) volume V_(max) size d₅₀ surface (μm) (mm³/g) (μm) (m²/g)Comparative 0.419 529 1.83 3.2 ATH OL-104 LE Comparative 1 0.353 5041.52 3.2 Comparative 2 0.303 615 1.61 4.0 Inventive ATH 0.277 439 1.894.9 grade no. 1

As can be seen in Table 1, the inventive aluminum hydroxide grade no. 1,an ATH according to the present invention, has the lowest median poreradius and the lowest maximum specific pore volume.

Example 3

By seeding a pregnant sodium illuminate liquor as e.g. disclosed in EP 1206 412 B1, a synthetic aluminium hydroxide grade with a median particlesize of d₅₀=2.43 μm and a specific surface of 2.6 m²/g was produced.Common separation and filtration techniques were used to separate saidsynthetic aluminum hydroxide; after subsequent washing steps on beltfilters, the resulting aluminum hydroxide filter paste with a solidcontent of 61 wt. % was liquefied by adding a sufficient quantity of thedispersing agent Antiprex A40 from Ciba until the viscosity of theslurry was about 150 cPoise. The slurry was fed into a pearl mill, typeKD 200 D from Bachofen/Switzerland. This mill contained 270 kg of smallbeads made of zirconium oxide with a diameter of 0.6 mm. The throughputof the mill was controlled so that after drying by means of a Niro F 100spray drier and conveying of the inventive aluminum hydroxide into asilo the resulting d₅₀ was 1.44 μm and the specific surface was 6.7m²/g. In the present example, the throughput was about 2 m³/h. FIG. 4shows the specific pore volume of the inventive aluminum hydroxide gradeno. 2 as a function of the applied pressure of the second intrusion testrun. FIG. 5 shows the specific pore volume of the inventive aluminumhydroxide grade no. 2 as a function of the pore radius. FIG. 6 shows thenormalized specific pore volume of the inventive aluminum hydroxidegrade no. 2 as a function of the pore radius on a linear scale. Theproduct properties of the inventive aluminum hydroxide grade no. 2 arecontained in Table 2, below.

Example 4 Comparative

The product properties of the comparative aluminum hydroxide gradeMartinal OL-107 LE produced by Martinswerk GmbH and the productproperties of the competitive aluminum hydroxide grade “Competitive 3”are also shown in Table 2.

TABLE 2 Maximum Median Specific Median pore specific pore particle BETradius (“r₅₀”) volume V_(max) size d₅₀ surface (μm) (mm³/g) (μm) (m²/g)Comparative 0.266 696 1.35 6.2 ATH OL-107 LE Comparative 3 0.257 6791.23 6.3 Inventive ATH 0.242 479 1.44 6.7 grade no. 2

As can be seen in Table 2, the inventive aluminum hydroxide grade no. 2has the lowest median pore radius and the lowest maximum specific porevolume.

Example 5

By seeding a pregnant sodium aluminate liquor as e.g. disclosed in EP 1206 412 B1, a synthetic aluminium hydroxide grade with a median particlesize of d₅₀=2.43 μm and a specific surface of 2.6 m²/g was produced.Common separation and filtration techniques were used to separate saidsynthetic aluminum hydroxide; after subsequent washing steps on beltfilters, the resulting aluminum hydroxide filter paste with a solidcontent of 61 wt. % was liquefied by adding a sufficient quantity of thedispersing agent Antiprex A40 from Ciba until the viscosity of theslurry was about 150 cPoise. The slurry was fed into a pearl mill, typeKD 200 D from Bachofen/Switzerland. This mill contained 270 kg of smallbeads made of zirconium dioxide with a diameter of 0.6 mm. Thethroughput of the mill was controlled so that after drying by means of aNiro F 100 spray drier and conveying of the inventive aluminum hydroxideinto a silo the resulting d₅₀ was 1.36 μm and the specific surface was10.0 m²/g. In the present example, the throughput was about 0.75 m³/h.FIG. 7 shows the specific pore volume of the inventive aluminumhydroxide grade no. 3 as a function of the applied pressure of thesecond intrusion test run. FIG. 8 shows the specific pore volume of theinventive aluminum hydroxide grade no. 3 as a function of the poreradius. FIG. 9 shows the normalized specific pore volume of theinventive aluminum hydroxide grade no. 3 as a function of the poreradius on a linear scale. The product properties of the inventivealuminum hydroxide grade no. 3 are contained in Table 3, below.

Example 6 Comparative

The product properties of the comparative aluminum hydroxide gradeMartinal OL-111 LE produced by Martinswerk GmbH are also shown in Table2.

TABLE 3 Maximum Median Specific Median pore specific pore particle BETradius (“r₅₀”) volume V_(max) size d₅₀ surface (μm) (mm³/g) (μm) (m²/g)Comparative 0.193 823 1.23 10.1 ATH OL-111 LE Inventive ATH 0.175 5881.36 10.0 grade no. 3

As can be seen in Table 3, the inventive aluminum hydroxide grade no. 3has a lower median pore radius and a lower maximum specific pore volume.

Example 7

396.9 g (100 phr) of ethylene vinyl acetate (EVA) Escorene™ UltraUL00119 from ExxonMobil was mixed during about 20 min on a two roll millW150M from the Collin company with 595.4 g (150 phr) of the inventivealuminum hydroxide grade no. 1 in a usual manner familiar to a personskilled in the art, together with 4.8 g (1.2 phr) of aminosilane AMEOfrom Degussa AG and 2.9 g (0.75 phr) of the antioxidant Ethanox® 310from Albemarle Corporation. The aminosilane ensures better coupling ofthe filler to the polymer matrix. The temperature of the two rolls wasset to 130° C. The ready compound was removed from the mill, and aftercooling to room temperature, was further reduced in size to obtaingranulates suitable for compression molding in a two platen press or forfeeding a laboratory extruder to obtain extruded strips for furtherevaluation. In order to determine the mechanical properties of the flameretardant resin formulation, the granules were extruded into 2 mm thicktapes using a Haake Polylab System with a Haake Rheomex extruder. Testbars according to DIN 53504 were punched out of the tape. The results ofthis experiment are contained in Table 4, below.

Example 8 Comparative

396.9 g (100 phr) of ethylene vinyl acetate (EVA) Escorene™ UltraUL00119 from ExxonMobil was mixed during about 20 min on a two roll millW150M from the Collin company with 595.4 g (150 phr) of the commerciallyavailable ATH grade OL-104 LE produced by Martinswerk GmbH in a usualmanner familiar to a person skilled in the art, together with 4.8 g (1.2phr) of aminosilane AMEO from Degussa AG and 2.9 g (=0.75 phr) of theantioxidant Ethanox® 310 from Albemarle Corporation. The aminosilaneensures better coupling of the filler to the polymer matrix. Thetemperature of the two rolls was set to 130° C. The ready compound wasremoved from the mill, and after cooling to room temperature, wasfurther reduced in size to obtain granulates suitable for compressionmolding in a two platen press or for feeding a laboratory extruder toobtain extruded strips for further evaluation. In order to determine themechanical properties of the flame retardant resin formulation, thegranules were extruded into 2 mm thick tapes using a Haake PolylabSystem with a Haake Rheomex extruder. Test bars according to DIN 53504were punched out of the tape. The results of this experiment arecontained in Table 4, below.

TABLE 4 Comparative with Inventive filler OL-104 LE no. 1 Melt FlowIndex @ 1.8 1.5 150° C./21.6 kg (g/10 min) Tensile strength (MPa) 12.913.4 Elongation at break (%) 221 214 LOI (% O₂) 36.2 38 Resistivitybefore water 3.1 × 10¹² 1.7 × 10¹² aging (Ohm · cm) Resistivity after 7d@70° C. 8.1 × 10¹¹ 8.4 × 10¹¹ water aging (Ohm · cm) Water pickup (%)1.25 1.67

As can be seen in Table 4, within the experimental error, the inventivealuminum hydroxide grade no. 1 has similar mechanical, rheological,electrical and flame retardant properties as the comparative gradeMartinal OL-104 LE.

Example 9

396.9 g (100 phr) of ethylene vinyl acetate (EVA) Escorene™ UltraUL00119 from ExxonMobil was mixed during about 20 min on a two roll millW150M from the Collin company with 595.4 g (150 phr) of the inventivefiller no. 2 in a usual manner familiar to a person skilled in the art,together with 4.8 g (1.2 phr) of aminosilane AMEO from Degussa AG and2.9 g (0.75 phr) of the antioxidant Ethanox® 310 from AlbemarleCorporation. The aminosilane ensures better coupling of the filler tothe polymer matrix. The temperature of the two rolls was set to 130° C.The ready compound was removed from the mill, and after cooling to roomtemperature, was further reduced in size to obtain granulates suitablefor compression molding in a two platen press or for feeding alaboratory extruder to obtain extruded strips for further evaluation. Inorder to determine the mechanical properties of the flame retardantresin formulation, the granules were extruded into 2 mm thick tapesusing a Haake Polylab System with a Haake Rheomex extruder. Test barsaccording to DIN 53504 were punched out of the tape. The results of thisexperiment are contained in Table 5, below.

Example 10 Comparative

396.9 g (100 phr) of ethylene vinyl acetate (EVA) Escorene Ultra UL00119from ExxonMobil was mixed during about 20 min on a two roll mill W150Mfrom the Collin company with 595.4 g (150 phr) of the commerciallyavailable ATH grade OL-107 LE produced by Martinswerk GmbH in a usualmanner familiar to a person skilled in the art, together with 4.8 g (1.2phr) of aminosilane AMEO from Degussa AG and 2.9 g (=0.75 phr) of theantioxidant Ethanox® 310 from Albemarle Corporation. The aminosilaneensures better coupling of the filler to the polymer matrix. Thetemperature of the two rolls was set to 130° C. The ready compound wasremoved from the mill, and after cooling to room temperature, wasfurther reduced in size to obtain granulates suitable for compressionmolding in a two platen press or for feeding a laboratory extruder toobtain extruded strips for further evaluation. In order to determine themechanical properties of the flame retardant resin formulation, thegranules were extruded into 2 mm thick tapes using a Haake PolylabSystem with a Haake Rheomex extruder. Test bars according to DIN 53504were punched out of the tape. The results of this experiment arecontained in Table 5, below.

TABLE 5 Comparative with Inventive filler OL-107 LE no. 2 Melt FlowIndex @ 1.1 1.25 150° C./21.6 kg (g/10 min) Tensile strength (MPa) 13.913.6 Elongation at break (%) 204 203 LOI (% O₂) 38.7 38.2 Resistivitybefore water 2.6 × 10¹² 1.5 × 10¹² aging (Ohm · cm) Resistivity after 7d@70° C. 6.3 × 10¹¹ 7.9 × 10¹¹ water aging (Ohm · cm) Water pickup (%)2.78 1.67

As can be seen in Table 5, within the experimental error, the inventivealuminum hydroxide grade no. 2 has similar mechanical, rheological,electrical and flame retardant properties as the comparative gradeMartinal® OL-107 LE.

Example 11

396.9 g (100 phr) of ethylene vinyl acetate (EVA) Escorene™ UltraUL00119 from ExxonMobil was mixed during about 20 min on a two roll millW150M from the Collin company with 595.4 g (150 phr) of the inventivefiller no. 3 in a usual manner familiar to a person skilled in the art,together with 4.8 g (1.2 phr) of aminosilane AMEO from Degussa AG and2.9 g (0.75 phr) of the antioxidant Ethanox® 310 from AlbemarleCorporation. The aminosilane ensures better coupling of the filler tothe polymer matrix. The temperature of the two rolls was set to 130° C.The ready compound was removed from the mill, and after cooling to roomtemperature, was further reduced in size to obtain granulates suitablefor compression molding in a two platen press or for feeding alaboratory extruder to obtain extruded strips for further evaluation. Inorder to determine the mechanical properties of the flame retardantresin formulation, the granules were extruded into 2 mm thick tapesusing a Haake Polylab System with a Haake Rheomex extruder. Test barsaccording to DIN 53504 were punched out of the tape. The results of thisexperiment are contained in Table 6, below.

Example 12 Comparative

396.9 g (100 phr) of ethylene vinyl acetate (EVA) Escorene™ UltraUL00119 from ExxonMobil was mixed during about 20 min on a two roll millW150M from the Collin company with 595.4 g (150 phr) of the commerciallyavailable ATH grade OL-111 LE produced by Martinswerk GmbH in a usualmanner familiar to a person skilled in the art, together with 4.8 g (1.2phr) of aminosilane AMEO from Degussa AG and 2.9 g (0.75 phr) of theantioxidant Ethanox® 310 from Albemarle Corporation. The aminosilaneensures better coupling of the filler to the polymer matrix. Thetemperature of the two rolls was set to 130° C. The ready compound wasremoved from the mill, and after cooling to room temperature, wasfurther reduced in size to obtain granulates suitable for compressionmolding in a two platen press or for feeding a laboratory extruder toobtain extruded strips for further evaluation. In order to determine themechanical properties of the flame retardant resin formulation, thegranules were extruded into 2 mm thick tapes using a Haake PolylabSystem with a Haake Rheomex extruder. Test bars according to DIN 53504were punched out of the tape. The results of this experiment arecontained in Table 6, below.

TABLE 6 Comparative with Inventive filler OL-111 LE no. 3 Melt FlowIndex @ 1.13 1.22 150° C./21.6 kg (g/10 min) Tensile strength (MPa) 15.715.2 Elongation at break (%) 183 185 LOI (% O₂) 38.6 39.6

As can be seen in Table 6, within the experimental error, the inventivealuminum hydroxide grade no. 3 has similar mechanical and rheologicalproperties as the comparative grade Martinal® OL-111 LE.

It should be noted that the Melt Flow Index was measured according toDIN 53735. The tensile strength and elongation at break were measuredaccording to DIN 53504, and the resistivity before and after waterageing was measured according to DIN 53482 on 100×100×2 mm³ pressedplates. The water pick-up in % is the difference in weight after wateraging of a 100×100×2 mm³ pressed plate in a de-salted water bath after 7days at 70° C. relative to the initial weight of the plate. The oxygenindex was measured according to ISO 4589 on 6×3×150 mm³ samples.

Example 13

The comparative aluminum hydroxide particles Martinal® OL-104 LE ofExample 2 and the inventive aluminum hydroxide grade no. 1 of Example 1were separately used to form a flame-retardant resin formulation. Thesynthetic resin used was a mixture of EVA Escorene® Ultra UL00328 fromExxonMobil together with a LLDPE grade Escorene® LL1001XV fromExxonMobil, Ethanox® 310 antioxidant available commercially from theAlbemarle® Corporation, and an amino silane Dynasylan AMEO from Degussa.The components were mixed on a 46 mm Buss Ko-kneader (L/D ratio=11) at athroughput of 25 kg/h with temperature settings and screw speed chosenin a usual manner familiar to a person skilled in the art. The amount ofeach component used in formulating the flame-retardant resin formulationis detailed in Table 7, below.

TABLE 7 Phr (parts per hundred total resin) Escorene Ultra UL00328 80Escorene LL1001XV 20 Aluminum hydroxide 150 AMEO silane 1.6 Ethanox 3100.6

In forming the flame-retardant resin formulation, the AMEO silane andEthanox® 310 were first blended with the total amount of synthetic resinin a drum prior to Buss compounding. By means of loss in weight feeders,the resin/silane/antioxidant blend was fed into the first inlet of theBuss kneader, together with 50% of the total amount of aluminumhydroxide, and the remaining 50% of the aluminum hydroxide was fed intothe second feeding port of the Buss kneader. The discharge extruder wasflanged perpendicular to the Buss Ko-kneader and had a screw size of 70mm. FIG. 10 shows the power draw on the motor of the discharge extruderfor the inventive aluminum hydroxide grade no. 1. FIG. 11 shows thepower draw on the motor of the discharge extruder for the comparativealuminum hydroxide grade OL-104 LE, produced by Martinswerk GmbH.

As demonstrated in FIGS. 10 and 11, variations in the energy (power)draw of the discharge extruder are significantly reduced when thealuminum hydroxide particles according to the present invention are usedin the flame-retardant resin formulation. As stated above, smallervariations in energy level allows for higher throughputs and/or a moreuniform (homogenous) flame-retardant resin formulation.

1. ATH particles having a median pore radius (“r₅₀”) in the range offrom about 0.09 to about 0.33 μm and a BET, as determined by DIN-66132,in the range of from about 1 to 15 m²/g.
 2. The ATH particles accordingto claim 1 wherein the maximum specific pore volume (“V_(max)”) of saidATH particles is in the range of from about 300 to about 700 mm³/g. 3.The ATH particles according to claim 1 wherein the V_(max) of said ATHparticles is in the range of from about 390 to about 480 mm³/g.
 4. TheATH particles according to claim 3 wherein the r₅₀ of said ATH particlesis in the range of from about 0.20 to about 0.33 μm.
 5. The ATHparticles according to claim 1 wherein the V_(max) of said ATH particlesis in the range of from about 400 to about 600 mm³/g.
 6. The ATHparticles according to claim 5 wherein the r₅₀ of said ATH particles isin the range of from about 0.185 to about 0.325 μm.
 7. The ATH particlesaccording to claim 1 wherein the V_(max) of said ATH particles is in therange of from about 450 to about 550 mm³/g, and the r₅₀ is in the rangeof from about 0.185 to about 0.25 μm.
 8. The ATH particles according toclaim 1 wherein the r₅₀ of said ATH particles is in the range of fromabout 0.09 to about 0.21 μm.
 9. The ATH particles according to claim 1wherein the V_(max) of said ATH particles is in the range of from about350 to about 550 mm³/g.
 10. The ATH particles according to claim 9wherein the r₅₀ of said ATH particles is in the range of from about 0.09to about 0.165 μm.
 11. ATH particles having: a) a BET specific surfacearea of from about 3 to about 6 m²/g; and a maximum specific pore volumeof from about 390 to about 480 mm³/g; or b) a BET specific surface areaof from about 6 to about 9 m²/g; and a maximum specific pore volume offrom about 400 to about 600 mm³/g; or c) a BET specific surface area offrom about 9 to about 15 m²/g; and a maximum specific pore volume offrom about 300 to about 700 mm³/g.
 12. The ATH particles according toclaim 11 wherein the oil absorption of a), b) or c), as determined byISO 787-5:1980, is in the range of from about 1 to about 35%.
 13. TheATH particles according to claim 11 wherein the oil absorption of a), b)or c), as determined by ISO 787-5:1980, is in the range of from about 23to about 30%.
 14. The ATH particles according to claim 11 wherein theoil absorption of a), b) or c), as determined by ISO 787-5:1980, is inthe range of from about 25 to about 32%.
 15. The ATH particles accordingto claim 11 wherein the oil absorption of a), b) or c), as determined byISO 787-5:1980, is in the range of from about 25 to about 35%.
 16. TheATH particles according to claim 11 wherein the oil absorption of a), asdetermined by ISO 787-5:1980, is in the range of from about 19 to about23%.
 17. The ATH particles according to claim 11 wherein the oilabsorption of b), as determined by ISO 787-5:1980, is in the range offrom about 21 to about 25%.
 18. The ATH particles according to claim 12wherein the d₅₀ of a), b) or c) is in the range of from about 0.5 toabout 2.5 μm.
 19. The ATH particles according to claim 12 wherein thed₅₀ of a) is in the range of from about 1.3 to about 2.0 μm.
 20. The ATHparticles according to claim 12 wherein the d₅₀ of b) is in the range offrom about 0.9 to about 1.8 μm.
 21. The ATH particles according to claim16 wherein the d₅₀ of a) is in the range of from about 0.5 to about 1.8μm.
 22. The ATH particles according to claim 17 wherein the d₅₀ of b) isin the range of from about 0.5 to about 1.8 μm.
 23. A flame retardedpolymer formulation comprising at least one synthetic resin and in therange of from about 5 wt % to about 90 wt % ATH particles having a) amedian pore radius in the range of from about 0.09 to about 0.33 μm; orb) a BET specific surface area of from about 3 to about 6 m²/g; and amaximum specific pore volume of from about 390 to about 480 mm³/g; or c)a BET specific surface area of from about 6 to about 9 m²/g; and amaximum specific pore volume of from about 400 to about 600 mm³/g; or d)a BET specific surface area of from about 9 to about 15 m²/g; and amaximum specific pore volume of from about 300 to about 700 mm³/g. 24.The flame retarded polymer formulation according to claim 23 whereinsaid synthetic resin is selected from thermoplastic resins,thermosetting resins, polymeric suspensions (latices), andpolyethylene-based resins.
 25. The flame retarded polymer formulationaccording to claim 24 wherein said synthetic resin is apolyethylene-based resin.
 26. The flame retarded polymer formulationaccording to claim 24 wherein said ATH particles have a d₅₀ in the rangeof from about 0.5 to about 2.5 μm.
 27. The flame retarded polymerformulation according to claim 24 wherein b) has: an r₅₀ in the range offrom about 0.185 to about 0.325 μm, a V_(max) in the range of from about450 to about 550 mm³/g, a BET specific surface area in the range of fromabout 6.5 to about 8.5 m²/g, an oil absorption in the range of fromabout 25% to about 32%, and a d₅₀ in the range of from about 1.3 toabout 2.0 μm.
 28. The flame retarded polymer formulation according toclaim 24 wherein c) has: an r₅₀ in the range of from about 0.09 to about0.21 μm, a V_(max) in the range of from about 350 to about 550 mm³/g, aBET specific surface area in the range of from about 10.5 to about 12.5m²/g, an oil absorption in the range of from about 25% to about 35%, anda d₅₀ in the range of from about 0.9 to about 1.8 μm.
 29. The flameretarded polymer formulation according to claim 24 wherein a) has: anr₅₀ in the range of from about 0.2 to about 0.3 μm, a V_(max) in therange of from about 410 to about 450 mm³/g, a BET specific surface areain the range of from about 3.5 to about 5.5 m²/g, an oil absorption inthe range of from about 23% to about 30%, and a d₅₀ in the range of fromabout 1.3 to about 2.5 μm.
 30. The flame retarded polymer formulationaccording to claim 26 wherein the oil absorption of said ATH particlesis in the range of from about 1 to about 35%.
 31. The flame retardedpolymer formulation according to any of claims 23 or 27-30 wherein saidflame retarded polymer formulation contains at least one additionaladditive selected from extrusion aids; coupling agents; dyes; pigments;fillers; blowing agents; deodorants; thermal stabilizers; antioxidants;antistatic agents; reinforcing agents; metal scavengers or deactivators;impact modifiers; processing aids; mold release aids, lubricants;anti-blocking agents; other flame retardants; UV stabilizers;plasticizers; flow aids; and the like.
 32. A molded or extruded articleformed from the flame retarded polymer formulation of claim
 31. 33. ATHparticles having an r₅₀ in the range of from about 0.2 to about 0.3 μm;in the range of from about 0.185 to about 0.25 μm; in the range of fromabout 0.09 to about 0.21 μm; or in the range of from about 0.09 to about0.165 μm.
 34. ATH particles having an r₅₀ in the range of from about0.09 to about 0.33 μm and a V_(max) in the range of from about 300 toabout 700 mm³/g.